Tension support mounting for a corona generating device

Abstract: A tension support mounting (89-98) for applying tension to the corona generating electrode (81) of a corona generating device (80). Various embodiments are described wherein the corona generating electrode is fastened to a mounting block (90) including an electrode support member (94), the position of which can be varied for applying variable tension to the corona generating electrode (81).

Description: The present invention relates generally to corona charging devices, and more particularly concerns a tension support mounting for supporting a corona generating electrode in a corona generating device utilized in electrostatographic applications. In electrostatographic applications, it is common practice to use corona generating devices for providing electrostatic fields to drive various machine operations. Such corona devices are primarily used to deposit charge on the photoreceptive member prior to exposure to the light image for subsequently enabling toner transfer thereto. In addition, corona devices are used in the transfer of an electrostatic toner image from a photoreceptor to a transfer substrate, in tacking and detacking paper to or from the imaging member by applying a neutralizing charge to the paper, and, generally, in conditioning the imaging surface prior to, during, and after toner is deposited thereon to improve the quality of the xerographic output copy. Because a relatively large number of corona generating charging devices are required to accomplish the many various operations in a single electrostatographic machine, a minor reduction in unit cost may reap significant cost advantages per machine, particularly in light of replacement cycles in a machine. In one type of charging device, a charging electrode may be provided in the form of an electrically conductive strip having projections, scalloped portions, or teeth members integrally formed with, and extending from, a longitudinal edge of the electrode. This arrangement provides significant structural and operational advantages over other types of electrode devices such as thin wire electrodes, including comparatively high structural strength and reduced levels of undesirable ozone emissions. In this respect, US-A-3,691,373 demonstrates a corona generating device generally comprising an electrically conductive electrode strip or pin array supported on either side by support strips, and mounted within an electrically nonconductive base member. One of the side strips is adapted for connection to an exterior connector from a high voltage source. The electrode is fixed into position within the base member by a plurality of transverse pins which fit through matching holes in the base member, the pin array, and the support strips. The corona generating device disclosed therein may further include a screen and/or an auxiliary electrode as well as various additional conductive shields for regulating charging current to control uniformity of charge. A detailed description and illustration of pin array corona generating devices, specifically describing the mounting mechanism used to support a pin array electrode in a corotron device is provided in US-A-4,725,732 and 4,792,680. Several problems have historically been associated with the unique design of pin array corona generating devices. Generally, it is important that the pin array electrode, which is typically stretched between mountings at opposite ends of the corona generating device, is maintained in taut condition. Any looseness and/or kinks in the electrode member may result in a non-uniform charge derived from the corona generating device. In order to insure that the electrode member is sufficiently supported, the pin array electrode is conventionally mounted between support members. as shown in US-A-4,725,732 and 4,792,680, previously referenced. It is also desirable in corona generating devices to provide an arrangement for easily replacing a deteriorated corona generating electrode upon failure, or preferably, for replacing a corona generating electrode prior to failure through preventative maintenance. Typically, the replacement of a pin array electrode necessitates replacement of the entire assembly of the corona generating device, creating waste and additional expense. Since replacement is usually handled by a service technician at the commercial site at which the machine is located, ease of replacement and adjustment in a minimum amount of time is essential. Thus, it is an object of the present invention to provide a pin array corona generating device that is cost effective and serviceable while eliminating waste by permitting the replacement and adjustment of the corona generating electrode within a corona generating device. US-A-4,110,811 discloses a corona generating device including a corona generating electrode in the form of a wire supported between insulating end block assemblies. Each assembly is constructed of mating half-sections which jointly define a substantially closed and insulated cavity lined with a conductive insert, wherein the electrode is held taut by means of a loaded compression spring carried within the insert on one half-section, the spring bearing against a conductive insert on the end and against a second conductive bead varied by the other end of the electrode. US-A-4,112,298 discloses a corona generating device including an electrically biased corona emitting wire supported adjacent its ends by insulating blocks. One of the blocks houses a coil spring, the loaded coil spring maintaining the wire in a taut condition. In accordance with one aspect of the present invention there is provided a corona generating device a corona generating device, comprising: an electrode member; and means for supporting said electrode member; and including a shield member having a pair of side shield elements and an endpiece connected therebetween, said electrode member being supported between said side shield elements, characterised by including means for selectively applying tension to said electrode member being supported by said supporting means, and in that the electrode member includes an elongated strip having an edge with an array of integral projections extending therefrom. Preferably, the electrode support means is integral with said mounting block. The mounting block may be slidably disposed between said side shield elements. The device may further include means for varying the position of said mounting block relative to said endpiece to permit selective application of tension to said electrode member. Preferably, the mounting block includes an integral support projection extending in a direction opposed to said shield member; and said shield member defines a support projection aperture adapted to receive said support projection so as to permit slidable movement of said mounting block within said shield member. The device preferably further includes means for urging said mounting block in a direction toward said endpiece to apply tension to said electrode member. Preferably, the urging means includes a resilient spring member coupled to said support projection and about a periphery of said endpiece. Alternatively, the mounting block may be pivotably mounted between said side shield elements. Preferably, the mounting block includes a pivot shoulder extending in a direction opposed to said shield member, said shield member defines a pivot aperture adapted to receive said pivot shoulder to permit pivotable movement of said mounting block within said conductive shield member. The device preferably further includes means for varying the position of said mounting block to permit selective application of tension to said electrode member. Preferably, the mounting block defines a threaded cavity, wherein said varying means includes an adjustment screw, in threaded engagement with said threaded cavity, for varying the position of said mounting block to permit selective application of tension to said electrode member. The mounting block may include a first member fixedly disposed between side shield elements; a second member slidably disposed between said side shield elements; and a resilient member for urging said first and second members in opposite directions. Preferably, said first member includes an alignment finger for aligning said electrode between said side shield members; and said second member includes an integral hook element for securing said electrode member thereto. Preferably, said first and second mounting block members each include an integral support projection extending in a direction opposed to said shield member; and said shield member includes a first support projection aperture for receiving said first mounting block member support projection in an interlocking manner so as to support said first member in a fixed position; and a second support projection aperture for receiving said second mounting block member support projection in a slidable manner to permit slidable movement of said second mounting block member within said conductive shield member. These aspects of the present invention will become apparent from the following description in conjunction with the accompanying drawings, in which: FIG. 1 is a perspective view of a prior art pin array corona generating device; FIG. 2 is a plan view in partial cross section of one embodiment of a tension support mounting for a corona generating device in accordance with the present invention; FIGS. 3 and 4 are plan and perspective views, respectively, of another embodiment of a tension support mounting for a corona generating device in accordance with the present invention; FIGS. 5 and 6 are plan views of yet another embodiment of a tension support mounting for a corona generating device in accordance with the present invention, showing the tension support mounting in a loosened and a tensioned position, respectively; FIGS. 7 and 8 are plan and perspective views, respectively, of still another embodiment of a tension support mounting for a corona generating device in accordance with the present invention. FIG. 9 is a schematic view showing an electrophotographic copying apparatus employing a corona generating device of the present invention. In the drawings, like reference numerals have been used throughout the several figures where possible to designate corresponding elements of various embodiments. An electrophotographic reproducing apparatus (see Fig.9) suitable for incorporating the corona generating assembly of the present invention is well known in the art, and a detailed description thereof has therefore been omitted from the present disclosure. For further details of such an apparatus, reference is made to USSN 08/000,762, a copy of which was filed with the present application, in which an exemplary reproducing apparatus is described with reference to Fig.9 thereof. Although the apparatus of the present invention is particularly well adapted for use in an electrophotographic reproducing machine, it will become apparent from the following discussion that the present corona generating device is equally well suited for use in a wide variety of electrostatographic processing machines as well as other systems requiring the use of a corona generating device. Thus, the invention is not necessarily limited in its application to the particular embodiment or embodiments shown herein. In particular, it should be noted that the corona generating device of the present invention, described hereinafter with reference to an exemplary charging system, may also be used in the toner transfer, detack, or cleaning subsystems of a typical electrostatographic copying or printing apparatus since such subsystems also require the use of a corona generating device. Referring to FIG. 1, there is shown a known configuration for a pin array corona generating device 80. This is described in detail in the above-mentioned USSN 08/000,762 with reference to Fig. 1 thereof. It will be understood that in the type of configuration disclosed in Fig. 1, any kind of looseness or kinks in the pin array electrode 81 will lead to non-uniform charging of the electrophotoreceptive belt or other surface to be charged, the present invention is directed to a tension mounting for supporting a corona generating electrode on an assembly similar to that shown in Fig. 1 of USSN 08/000,762. Slackness also results in non-uniform spacing of the electrode from the surface and increases the chances of vibration being set up in the electrode while operating. In order to alleviate the problem of non-uniform charging due to these causes, an arrangement is provided by the present invention to selectively provide a predetermined tension in the electrode while also allowing tension to be released for removal and replacement of the electrode in the corona generating device 80. Referring now more particularly to FIGS. 2 - 8, an exemplary embodiment of corona charging device 80, incorporating the specific features and the subject matter of the present invention, is illustrated and will be described in greater detail. As in the prior art device, the primary components of the corona charging device 80 are pin array electrode 81, side shield members 86, and end mounting blocks 87 and 88, as shown in FIG. 1. In a preferred embodiment of the present invention. at least one end mounting block of the corona charging device 80, for example end mounting block 88, includes a tension support mounting in accordance with the present invention. While the present description will proceed under the assumption that the end mounting block opposite the tension support mounting of the present invention operates to receive the electrode 81 in a fixed mounting position as is known in the art, it is contemplated that the corona generating device may include a pair of tension support mountings in accordance with the present invention positioned at opposite ends of the corona generating device for supporting the electrode between the side shield members 86. Moving now, initially, to the exemplary embodiment of FIG. 2, the illustrated embodiment shown thereat comprises a mounting block 90 disposed between side shield elements 86, adjacent an endpiece 89 for connecting the side shield elements 86. Although endpiece 89 is shown as a connecting piece located on a plane parallel with the pin array electrode 81, the endpiece 89 may alternatively be positioned in a plane perpendicular to the pin array 81 in a configuration similar to that shown in FIG. 1, adjacent to mounting block 88. In the particular embodiment of FIG. 2, the mounting block 90 includes a pair of support projections 92 extending in a direction opposed to the side shield elements 86 for cooperative engagement with support projection apertures 93, as may be more clearly understood by reference to FIGS. 4 and 8 showing alternative embodiments of the present invention in perspective view. The support projection apertures 93 operate in combination with the support projections 92 to maintain the mounting block 90 in fixed position between side shield elements 86. A threaded screw hook 94 including a threaded shaft 96 and a hook segment 95 as well as a cooperatively threaded mounting nut 98 are also provided. Mounting block 90 also includes a channel 97 for allowing passage of the pin electrode 81 to the hook segment 95 and an alignment finger 91 projecting into channel 97 for contacting the pin electrode 81 to align the electrode between the side shield elements 86. In the embodiment of FIG. 2, the electrode 81 is secured to the hook segment 95 of threaded hook screw 94 which acts as a means for supporting the electrode 81. Mounting nut 98 is threaded onto threaded shaft 96, and pushes against mounting block 90 to selectively position the hook segment 95 relative to the fixed position of the mounting block 90. Thus, the tension support mounting of the present embodiment applies tension to the pin array electrode 81 by means of tightening mounting nut 98. A specified tension can be applied by tightening mounting nut 94 to a predetermined torque setting. Conversely, tension on the pin array electrode 81 can be reduced by loosening mounting nut 98. In this manner, the tension support mounting of the present invention can be used to remove the pin array electrode 81 from the corona generating apparatus in order to for example, replace the pin array electrode 81. Preferably, the mounting block 90, as well as threaded screw hook 94 and nut 98 of this embodiment of the present invention are fabricated from a high strength insulator such as polyvinyl fluoride for preventing arcing or other current flow beyond the periphery of the corona generating device. Alternatively, the threaded screw hook 94 may be fabricated from a highly conductive material for coupling the electrode 81 to a high voltage power supply (not shown) for application of a corona generating potential to the pin array electrode 81. It is noted, however, that if threaded screw hook 94 is fabricated from a conductive material, the portion of threaded segment 96 which extends beyond mounting nut 98 must be properly insulated or located far enough from any other conductive part of the charging device, as well as any other conductive part in the machine environment, so as not to provide a potential corona forming surface or any potentially hazardous conditions. An alternative embodiment of the present invention is illustrated in FIGS. 3 and 4, wherein mounting block 90 includes an integral hook element 105 extending into channel 97 for receiving and securing the pin array electrode 81 thereto to support the electrode between the side shield elements 86, in a manner similar to that shown and described with respect to the embodiment of FIG. 2. As in the previous embodiment, the mounting block 90 also includes an alignment finger 91 protruding into channel 97 for aligning the pin array electrode 81 between side shield members 86. The mounting block 90 also includes a pair of support projections 102 opposing side shield elements 86. Side shield elements 86 include cooperative support projection apertures 103 having a lengthwise dimension greater than the dimension of the support projection 102 for permitting limited longitudinal travel of mounting block 90 within the conductive shield of corona generating device 80. As such, mounting block 90 is slidably disposed within the conductive shield of the corona generating device 80. The tension support mounting of this embodiment further includes a resilient spring member 108 attached to each support projection 102 and extending about the periphery of the corona generating device 80. As such, the resilient spring member 108 supplies a force for urging the mounting block toward the end of the corona generating device, thereby applying tension to the pin array electrode 81. Conversely, the spring member 108 can be detached from a support projection for releasing tension on the electrode 81 and permitting replacement thereof. It will be understood that various spring members having various lengths or tensioning strength can be utilized to permit selective application of tension to electrode member 81. In another alternative embodiment of the present invention, as shown in FIGS. 5 and 6. mounting block 90 includes an integral hook element 115 and an alignment finger 91 both extending into channel 97. The mounting block has a dimension that is substantially less than the lateral dimension separating side members 86. In this embodiment, mounting block 90 includes a pivot shoulder 112 extending through a pivot aperture 113 located in one of the shield members 86. The tension support mounting of this embodiment also includes a tension screw 118 extending through the shield member 86 adjacent the pivot aperture 113 for being threaded into a threaded cavity 116 in the mounting block 90. In this embodiment, the tension screw 118 is threaded into the threaded cavity 116 in mounting block 90 for pivoting the mounting block 90 about pivot shoulder 112, thereby drawing the surfaces of the mounting block 90 and the shield member 86 into abutting contact with one another as shown in FIG. 6. The variable pivoting action of this embodiment provides means for applying selective tension to the pin array electrode 81. Yet another alternative embodiment for implementing the objectives of the present invention is shown in FIGS. 7 and 8, wherein the tension support mounting comprises two cooperative mounting block members 119 and 120 individually mounted between side shield elements 86 in a fixed and slidable configuration, respectively. Each mounting block member includes a channel 97 while the fixed mounting block member includes alignment finger 91 and the slidably mounted mounting block member 120 includes an integral electrode receiving hook 125 for supporting electrode 81. Fixedly mounted member 119 includes a pair of support projections 121 extending into support projection apertures 123 and slidably mounted member 120 includes support projections 122 which extend into support projection apertures 124. A pair of resilient spring members 127 are provided between the fixed and slidably mounting block members mounted into cooperative receiving pockets 128 such that the slidable block 120 is urged away from the fixed block 119 to thereby provide a tensioning force to the pin electrode to pull the electrode firmly taut. As in the embodiment of FIGS. 5 and 6, it will be understood that various spring members having various lengths or compression characteristics can be utilized to permit selective application of tension to the electrode 81. In recapitulation, it should be clear from the foregoing discussion that the present invention provides various embodiments of a novel.mounting apparatus for applying tension to an electrode in a corona generating device. The electrode is secured to an electrode support member which is capable of being selectively positioned so as to permit selective application of tension to the electrode. The novel mounting apparatus maintains the electrode in a taut formation within the corona generating device and allows for on-site adjustment and replacement of the electrode rather than replacement of the entire corona generating device assembly.

Claims: A corona generating device, comprising: an electrode member (81); and means (90; 119) for supporting said electrode member; and including a shield member having a pair of side shield elements (86) and an endpiece (89) connected therebetween, said electrode member being supported between said side shield elements, characterised by including means (94-98; 102-108; 112-118; 124-128) for selectively applying tension to said electrode member being supported by said supporting means, and in that the electrode member includes an elongated strip having an edge with an array of integral projections extending therefrom. The corona generating device of claim 1, wherein said tension applying means includes: a mounting block (90; 119) disposed adjacent said endpiece (89) between said side shield elements (86); and electrode attachment means (95; 105; 115; 125) for securing said electrode member (81) to said mounting block, said electrode attachment means being selectively positionable within said shield member. The corona generating device of claim 2, wherein said mounting block (90;119) includes a channel (97) for receiving said electrode member (81), said electrode attachment means (95; 105; 115; 125) being disposed in said channel (97). The corona generating device of claim 3, wherein said mounting block (90; 119) further includes an alignment finger (91) projecting into said channel (97) for contacting said electrode member (81) to align said electrode member between said side shield elements (86). The corona generating device of claim 2, 3 or 4, with said mounting block (90) being disposed in a substantially fixed position between said side shield elements (86). said electrode support means (96,98;102,105; 112,113,116,118; 120,122,124,127) for varying the position thereof relative to said mounting block (90;119)to permit selective application of tension to said electrode member (81). The corona generating device of any of the preceding claims, wherein said electrode support means includes: a threaded screw hook (94) comprising a threaded shaft (96) and a hook segment (95) integral therewith, said electrode member (81) being secured to said hook segment; and a threaded nut (98) cooperative with said threaded shaft for situating said hook segment into a selected position relative to said mounting block so as to apply selective tension to said electrode member secured to said hook segment. The corona generating device of any of the preceding claims, wherein: said electrode attachment means (95; 105; 115; 125) comprises an insulative material; and said mounting block (90; 119) comprises an insulative material for electrically isolating said electrode member. The corona generating device of any of 1 to 6, wherein said electrode support means comprises a conductive material for conducting an electrical biasing potential to said electrode member. The corona generating device of any of the preceding claims, wherein: said mounting block (90;119) includes an integral support projection (92; 121) extending in a direction opposed to said shield member (86,89); and said shield member defines a support projection aperture (123) for receiving and locking said support projection so as to support said mounting block in a substantially fixed position. An image reproduction machine incorporating the corona generating device of any of the preceding claims.

Inventors: CARYL BRUCE D, GROSS ROBERT A, CARYL, BRUCE D., GROSS, ROBERT A.
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1994
Main classification: G03G15
IPC codes: H01T19, G03G15